​ Hundreds of above-ground nuclear tests were conducted in Nevada in the 1950’s and the early 1960’s. The wind carried the radioactive fallout, including Strontium-90, across the country. It settled on the grass and in the water and was consumed by dairy cows. High levels of Strontium-90 then appeared in our milk supply.​ The St. Louis Baby Tooth Survey was done to determine just how much radiation children were absorbing. Strontium-90 settles in bone and teeth and shed teeth are easy to collect. A total of over 300,000 teeth were donated by children from 1959-1970. Early results of the study helped convince President Kennedy to sign a treaty banning above-ground nuclear tests.